The broad objectives of the program are: (1) To study the possibility of simulating in the laboratory the type of chemical processes that are involved in the key step in the biogenesis of naturally occurring cyclic terpenoids, including the steroids. This key step is the cyclization process which proceeds, in vivo, with extraordinary structural- and stereospecificity; (2) to examine systems which are designed to shed light on the intimate mechanism of the key cyclization step in the aforementioned biosyntheses; (3) to attempt to apply biomimetic cyclizations to the total synthesis of polycycloisoperenoid systems, particularly the steroids. This study envisages a basically new synthetic approach to natural products of importance in medicine and life processes; (4) to exploit any especially novel behavior or reactions encountered in the process of the aforementioned studies. Detailed plans are given for applying the aforementioned biomimetic polyene cyclizations to the synthesis of: (a) lanosterol types; (b) retro steroid analogs; (c) corticoid antiinflammatory agents; (d) 19-norsteroidal oral contraceptives; (e) protosterol types involved in steroid biogenesis; and (f) vitamin D3 metabolites and analogs involved in control of calcium and phosphorus metabolism. Other projects include designs for (g) elucidating the mechanism of polyene cyclizations; (h) developing enzyme models for polyene cyclizations; and (i) using cationic cyclizations to produce hydroazulene and longifolene structures. The areas that are of more basic and theoretical concern, e.g., (e), (g) and (h) are scheduled for study under anticipated NSF funds.